The production of a major portion of agricultural crops in the Western United States depends upon irrigation, since natural precipitation is insufficient to support anything other than, for example, natural grassland grazing or winter wheat. Water for irrigation may come from a number of sources, including surface impoundments (such as lakes and reservoirs), canals, deep wells, and the like. In many of these applications, especially in the use of surface water, the water stream naturally entrains a significant quantity of solid debris
Irrigation water from wells may contain substantially less organic contaminants (such as vegetable matter--weeds, grass, etc.) than does surface water, while both sources of water may contain significant quantities of inorganic contaminants, such as sand. In almost all cases, the irrigation water must be pumped, and it is then often applied to the crop land through sprinklers. When such water is directed through pumps, both the organic and inorganic contaminants may clog up the pump mechanism. Whether or not pumps are or may be clogged by such contaminants, virtually all sprinkler systems are susceptible to clogging with either the heavier inorganic or the lighter inorganic materials.
For years the only method of filtering such materials from irrigation water comprised a simple screen against which the water stream was directed. While such screens work on a gross level, constant supervision is necessary to assure cleaning when/if they became plugged. Later, technology was developed to make essentially automatic operation of such filters possible.
A number of United States patents illustrate representative attempts to solve the problem of removing debris from irrigation water. For example, in U.S. Pat. No. 5,132,013, a perforated frusto-conical filter apparatus is positioned within a housing such that unfiltered irrigation water is directed into the filter. Filtered water is discharged through the filter and out an exit. The bottom of the filter is open so that heavier materials will settle out by gravity, and a drain plug is provided to clean the filter. For cleaning the filter, the device is isolated and the filter media is removed therefrom to remove debris from the perforated filter. In U.S. Pat. No. 3,959,140, a filter device is disclosed that comprises an outer housing with a cylindrical perforated filter therein. Irrigation water is directed into the filter, which then passes through the filter and is discharged. A brush device is provided inside the filter which permits the inner surface of the filter to be cleansed, either manually or automatically. A drain is located at the lowermost end of the housing. Pressure sensing devices are provided so that when a sufficient pressure differential between the outside and inside of the filter within the housing is sensed (an indication of a plugged filter), the water outlet is closed and the drain is opened. The brush is then activated and matter adhered to the inside of the screen is flushed away.
Finally, a conical filter member (small end down) within a housing is disclosed in U.S. Pat. No. 4,043,915. Water is directed into the larger upper end and as it is passed through the filter media, solids entrained in the water are concentrated in the lower, smaller end thereof. A drain flushes away these solids, which are carried to a settling container, where the solids are further concentrated and removed.
While the above-noted devices perform their intended function to some degree, it is clear to those skilled in this art that an improved filter device is needed which can filter large quantities of water having relatively large concentrations of solid debris therein, all the while having the capability to automatically or easily be cleaned without disassembling the device.